NC Viper is operating P25 Phase I so no matter what you get, it should cover them easily.
As for TN and GA, look at a scanner that does P25 Phase II, there are some agencies using TDMA and a phase II scanner will be needed.
I've been using a Uniden BCD436HP to monitor TACN from Bradley County area for two years. In December, I purchased a Whistler TRX-1. So far, the Uniden is outperforming the Whistler, as far as digital decoding is concerned. I'm hearing far more from the "robot" on the Whistler. If you're accustomed to programming an object based scanner such as the Pro106, the Whistler TRX-1 will remind you of a shoe that fits. Learning to program the BCD436HP is, at best, difficult. If you live in a rural area and want to be able to monitor Volunteer Energy during power outages, the TRX-1 is a must. It's NXDN clarity is much better than even the revered AOR DV-1.